This isn't just red lines not being crossed. As it turns out, from the commentary, the EU has done it again... they convinced Boris to swallow a deal that's shittier than May's and force him to either throw the DUP under the bus or lose the vote in the Commons. Either way, he can't blame the EU, because the EU already signalled agreement today.
How they managed to pull this off, no idea... but that's why we have them.